1. Field of the Invention
The present invention relates to a tungsten film coating method using tungsten oxide (WO3 or WO2.9) powders, and more particularly, to a method of coating a tungsten thin film a few nanometers (nm) to tens of micrometers (xcexcm) thick on a metal substrate using a chemical vapor transport (CVT) reaction preferring to occur on the metal substrate. In this case, the CVT reaction occurs in a following manner. First of all, when the tungsten oxide powders are reduced to pure tungsten under a hydrogen atmosphere, solid phase of the tungsten oxide powders is changed into vapor phase, experiences diffusion so as to move to the metal substrate, and then changed into the solid phase again so as to be deposited thereon.
2. Background of the Related Art
As a method of coating a tungsten thin film on a metal substrate, chemical vapor deposition (CVD) by decomposing of WF6 gas or physical vapor deposition (PVD) by sputtering of pure tungsten target is widely used so far. However, the CVD process is disadvantageous in that WF6 as a reactant is toxic as well as HF is formed as a product so as to bring about environmental pollution. Besides, the PVD process requires the expensive tungsten target material as well as a high-vacuumed equipment of precision.
The present inventors have made many efforts to overcome the above-mentioned disadvantages or problems, and have developed a method of coating a tungsten on various metal substrates using a simple reduction treatment technique under a hydrogen atmosphere while the metal substrate is kept being contacted with tungsten oxide powders. Different from the method according to the related art, the method according to the present invention generates water as a product instead of toxic gas and enables to coat tungsten using a furnace operation under a reduction atmosphere without the expensive equipments.
Accordingly, the present invention is directed to a tungsten film coating method using tungsten oxide powders that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a method of coating a tungsten thin film on a metal substrate using the phenomenon of tungsten migration through vapor phase when thermal reduction treatment is carried out on tungsten oxide powders without using previous chemical or physical deposition requiring expensive precision equipments or causing environmental pollution.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a tungsten film coating method using tungsten oxide powders according to the present invention includes the steps of contacting the tungsten oxide powders with a metal substrate and carrying out thermal reduction treatment thereon at a temperature of at least 650xc2x0 C. under a hydrogen atmosphere just to coat the tungsten film on the metal substrate.
Preferably, the metal substrate is selected from the group consisting of Cu, Fe, Ni, Co, Cr, and W substrates.
Preferably, the tungsten film is coated 500 nmxcx9c25 xcexcm thick by carrying out thermal reduction treatment for 10 minutes to six hours at a temperature range between 650xcx9c1050xc2x0 C.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.